The invention relates to an electrostatic manipulating apparatus.
For transmission electron microscope (TEM) analysis, micro-samples are removed from semiconductor wafers by a combination of a scanning electron microscope (SEM) and focused ion beam (FIB). This is realized with a focused ion beam to cut the sample and a SEM for determination of the location of the region of interest. Subsequently the samples are taken outside the vacuum chamber and placed under an optical microscope on a TEM sample holder. The size of the samples is usually about 15 to 20 xcexcmxc3x975 xcexcmxc3x970.1 to 1 xcexcm. This is a rather time-consuming operation in which samples may be damaged or get lost.
In order to increase the reliability and the productivity an automated sampling apparatus would be desirable, that will perform all required operations under one and the same vacuum, thus avoiding any possible effects of being exposed to the atmosphere (in particular oxygen, water vapour and the like). In addition such an automatic apparatus would permit a more accurate action and a faster production.
In U.S. Pat. No. 5,270,552 it is described that a micro-sample may be removed from a wafer by means of a fine probe which is attached to the sample by a beam-induced deposition film. This method has the disadvantage that the deposition film introduces a possible contaminant which is undesirable in the semiconductor fabrication environment. Moreover, a fine probe is very fragile and susceptible to damage by collision with the wafer or sample surface.
European Patent Application EP 0 927 880 A1 describes a method and apparatus for preparing samples whereby, as illustrated by FIG. 13, a probe is firmly joined to a micro-specimen by using an electrostatic absorption technique. In this respect it is observed that said method has the merit that there is no accompanying chemical change in quality and that no accompanying contamination is introduced in the wafer or the sample. However, it has a significant disadvantage due to the fact that the position and orientation of the sample, once attached to the probe, is undefined. As a consequence, serious difficulties are encountered in attempting to attach the sample to a support in such a way that it is suitable for TEM observation and analysis.
The present inventor has recognized that advantages may be attained by handling samples in a stable, fully controlled manner, thus allowing a stable procedure. The inventor has also recognized that in addition the procedure might be automated, thus providing a substantial advantage over any prior art method.
In consequence, amongst other things, it is an object of the invention to provide an apparatus for handling a sample during and after removal from semiconductor wafers under a continuous vacuum without introducing foreign material while the sample is maintained in a stable position. Therefore, according to one of its aspects the invention is characterized in conformity with the characterizing part of claim 1. Further advantageous aspects of the invention are disclosed in the dependent claims.